1. Field of the Invention
The present invention relates to an equipment designed to enable a travelling device called "pig" to pass through a flow line of a product that can form deposits on said line and cause clogging or other problems, such as a flow load loss.
More specifically, the invention is an equipment which, when installed at any intermediate point of a product flow line system, enables a pig introduced into an opening of one of the lines, referred to as an "inlet connection" to run through said line up to a point where, under the effect of a control by a valve specially located at a return curve on the equipment provided by the invention, it can return through a different line, to be cleared, and be withdrawn, after the removal of the material dragged along by the pig, through an opening referred to as an "outlet connection".
2. Description of the Prior Art
The line cleaning device called pig is a piece usually made of a polymeric elastomer (it can also be made of other, less appropriate materials, including metal) and having a widely-varying shape, usually cylindrical (it can also be spherical), or comprising several flexible discs, connected by a flexible, plastic or pivoted, metal shaft, being provided or not with abrasive members intercalated. Such device is inserted in a place in the piping and, afterwards, fluid pressure (gas or liquid) is applied, driving intensively said pig in its travel inside the piping, where it drags to the end of the piping (or to an intermediate point for removal) the undesirable material deposited on the internal walls of the piping.
The term employed to designate the travelling device introduced inside the piping is the English word "pig" of a controversial origin. However, as the Brazilian Portuguese term chosen, especially for purchasing purposes on the Brazilian market, "raspador" (scraper), does not properly define the object, experts in this field have opted for the English word, which is universally accepted. For this reason, said "travelling" object is here simply designated as "pig".
On deep-water well oil flowlines leading to certain points on the surface (such as a platform), when an obstruction is formed by the accumulation of materials such as "paraffin", there is no physical condition of sending a cleaning pig and recovering it because the "final" portion of the piping is in deep waters. In cases where such cleaning is imperative, a common solution in the art has been to remove (with a lot of work and at a great cost) the piping to the surface and to replace it with a new one, and the obstructed piping should be cleaned on the surface by convenient methods, including the use of pigs made of polymeric material.
To overcome this obstacle, the prior art has developed, among other concepts not relevant for understanding the present invention., the pig passing concept referred to as "pigging loop". However, within this concept, the current practice only provides for the connection of two lines having the same diameter incorporated into the design of an under-sea equipment close to an oil-producing well (e.g., a Christmas tree or a template manifold), so that a pig is sent through one of them and is returned through the other. With this design option, the production line has, compulsorily and permanently, the same diameter as the water and/or gas injection line (or a secondary production line or also an additional service line ).
Although progress has been made to facilitate pig operations in pipings having portions that are difficult to reach, such as the offshore oil production pipings already described, there remains the drawback of little operational flexibility, for it requires definitive modifications to the internal design of said undersea equipment (e.g., a Christmas tree or a template manifold) and lines having the same diameter, for the pig circulation, even in those cases where such pig is not necessary in view of the inherent characteristics of the fluid being carried, thus causing a significant and, above all, unnecessary increase in the costs of offshore oil-producing systems. It cannot be used either on systems already existing when the undesirable deposit formation appears late on said undersea piping, for it would force the full replacement of the whole producing system, including the fixed production equipment, causing serious losses.